U.S. patent application number 17/285652 was filed with the patent office on 2021-12-23 for security element for a valuable document, method for producing same and valuable document that comprises it.
This patent application is currently assigned to OBERTHUR FIDUCIAIRE SAS. The applicant listed for this patent is OBERTHUR FIDUCIAIRE SAS. Invention is credited to Xavier Borde, Guillaume Chapeau, Julien Gillot.
Application Number | 20210394547 17/285652 |
Document ID | / |
Family ID | 1000005870277 |
Filed Date | 2021-12-23 |
United States Patent
Application |
20210394547 |
Kind Code |
A1 |
Borde; Xavier ; et
al. |
December 23, 2021 |
Security Element For A Valuable Document, Method For Producing Same
And Valuable Document That Comprises It
Abstract
The present invention relates in particular to a security
element (1) for a valuable document, which comprises an array (R)
of at least two contiguous or adjacent lines (2, 2', 2''), at least
one of these lines (2) being raised and having two opposing and at
least partially inclined sides (20, 21) that each originate along
one of the longitudinal and opposing edges (200, 210) of the line
(2), characterised by the fact that the two opposing inclined
flanks (20, 21) meet at a single, uninterrupted, sinuous junction
area (22), that extends in the longitudinal direction of the line
(2), the sides (20, 21) having no discontinuities or interruptions
at least in the longitudinal direction.
Inventors: |
Borde; Xavier; (Osse,
FR) ; Gillot; Julien; (Chateaugiron, FR) ;
Chapeau; Guillaume; (Erce Pres Liffre, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
OBERTHUR FIDUCIAIRE SAS |
Paris |
|
FR |
|
|
Assignee: |
OBERTHUR FIDUCIAIRE SAS
Paris
FR
|
Family ID: |
1000005870277 |
Appl. No.: |
17/285652 |
Filed: |
October 22, 2019 |
PCT Filed: |
October 22, 2019 |
PCT NO: |
PCT/EP2019/078765 |
371 Date: |
April 15, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B42D 25/324 20141001;
B42D 25/328 20141001; G02B 5/1861 20130101 |
International
Class: |
B42D 25/324 20060101
B42D025/324; B42D 25/328 20060101 B42D025/328; G02B 5/18 20060101
G02B005/18 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 22, 2018 |
FR |
1859737 |
Claims
1. A security element for a valuable document, which comprises an
array of at least two contiguous or adjacent lines, each of said
lines comprising longitudinal and opposite edges, at least one of
these contiguous or adjacent lines being in relief and having two
opposite flanks, at least one of which is partly inclined, wherein
each of said opposite flanks originate along one of said
longitudinal and opposite edges of said line, and wherein said two
opposite inclined flanks meet at a single and uninterrupted
sinuous-shaped junction area which extends along the longitudinal
direction of said line, said opposite flanks (20, 21) having no
discontinuity or interruption at least in said longitudinal
direction.
2. The element according to claim 1, wherein said junction area has
the shape of a sinusoid.
3. The element according to claim 2, wherein said sinusoid has an
unchanged period over its entire extent.
4. The element according to claim 2, wherein said sinusoid has at
least one period variation over its extent.
5. The element according to claim 1, wherein said array has a
non-periodic structure.
6. The element according to claim 1, wherein the relief of said at
least two lines has a non-periodic variation over its extent.
7. The element according to claim 1, wherein said junction area is
parallel or substantially parallel to the plane in which said two
longitudinal and opposite edges are contained.
8. The element according to claim 1, wherein said junction area is
perpendicular or substantially perpendicular to the plane in which
said two longitudinal and opposite edges are contained.
9. The element according to claim 7 or 8, wherein that the
amplitude of said junction area is variable.
10. The element according to claim 1, wherein the spacing between
said junction area and the plane in which said longitudinal edges
are contained is constant or variable.
11. The element according to claim 1, wherein said junction area
consists of a ridge or preferably a stripe.
12. The element according to claim 1, wherein at least one of said
flanks has a rectilinear or non-rectilinear slope.
13. The element according to claim 1, wherein all said lines of
said array have an identical width.
14. The element according to claim 1, wherein at least two lines of
said array have a non-triangular relief profile in width and/or in
length.
15. The element according to claim 1, wherein at least one line of
said array has a width different from that of the other lines.
16. The element according to claim 1, wherein at least one line of
said array has a junction area of a different shape from that of
the other lines.
17. The element according to claim 1, wherein said flanks are
inclined upwards or downwards, relative to said longitudinal and
opposite edges.
18. The element according to claim 1, wherein it comprises a
multilayer assembly, wherein said array is integrated in said
multilayer assembly, and wherein said multilayer assembly comprises
additional layers which are chosen from the group consisting of the
dye or pigment inks, the color-changing pigment inks, the liquid
crystals, the multilayer plastic films with refractive index
variation, the optical interference filters with thin layers, the
vacuum-deposited metals.
19. A method for manufacturing an embossing tool of a security
element according to claim 1, wherein it comprises at least the
steps consisting in: a) making, i.e. manufacturing a
two-dimensional image characteristic of a fraction of a line of
said array, this image having multiple levels of gray, a depth or
an altitude being assigned to each gray level; b) repeating step a)
as much as necessary and assembling identical or different
fractions to form a line of the desired shape and length; c)
repeating steps a) and b) as much as necessary to make lines to be
assembled in a contiguous or adjacent manner in order to form
sub-assemblies; d) if necessary, repeating steps from a) to c) so
as to achieve the final pattern; e) from the image or the final
pattern derived from steps a) to d) above, forming a
three-dimensional image in which each point of this image has a
location characteristic of said gray level; f) proceeding with the
three-dimensional hardware production thereof, so as to obtain an
imprint characteristic of the image derived from step e).
20. The method according to claim 19, wherein said origination is
carried out by implementing either of the following techniques:
photolithography, in particular gray-level photolithography, laser
lithography, electronic lithography or electron-beam
lithography.
21. A valuable document, in particular banknote, which includes at
least one security element according to claim 1.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a security element for a
valuable document. It also concerns a manufacturing method such a
security element as well as a valuable document which includes at
least such a security element.
TECHNOLOGICAL BACKGROUND OF THE INVENTION
[0002] Securities called first-level securities, i.e. those that
are visible without additional equipment, are effective bulwarks
against counterfeit security documents or valuable documents such
as banknotes.
[0003] Also, the manufacturers of this type of documents
concentrate on the achievements of these securities by making sure
that they remain very intuitive in their operation but complex to
achieve without the know-how and the appropriate equipment and, of
course, impossible to counterfeit. This implies that the
technologies used for their achievement are difficult to access for
the general public and that the implementation of these tools is
restricted and/or dedicated to the specific trades in securing
documents.
[0004] Indeed, these are elements that can be easily authenticated
by everyone and that allow everyone to authenticate a document such
as a banknote.
[0005] Document FR-A-2942811 discloses a technique of formation of
a security element comprising an array of relief lines, each
including at least one flank whose angle of inclination varies
gradually along this line so as to form in light reflection a
degraded optical effect which changes according to the viewing
angle of this element.
[0006] This document teaches in particular the production of a
plate for intaglio printing made by means of a laser engraving or a
precision mechanical milling tool including in negative the array
of lines mentioned above.
[0007] This plate is used as a means for embossing a paper-type
medium including a reflective surface, for example of the
iridescent ink or color-changing ink type. In an alternative mode,
it is also possible to cover (coat) a previously embossed surface
with ink.
[0008] More particularly, the width of a line of the array is
comprised between 10 .mu.m and 2 mm and preferably between 100
.mu.m and 1 mm, with a height comprised between 0 and 200
.mu.m.
[0009] In practice, there are used a line width of 400 .mu.m and a
height varying from 0 to 100 .mu.m with a pitch, i.e. the minimum
displacement of the engraving tool and a laser "spot" size
(effectively active engraving area) which correspond to the
resolutions of the engraving tools conventionally used for the
intaglio engraving of plates.
[0010] These dimensions are of course calculated to allow obtaining
a visual effect when the document is inclined, preferably by an
angle on the order of +90.degree. to -90.degree., and more
preferably by an angle on the order of +30.degree. to -30.degree.
which corresponds to the classic inclination of a banknote upon its
inspection.
[0011] This security element is effective over a portion on the
order of 2 cm.sup.2, it being understood that the term "portion"
means the recommended surface on which the system extends in order
to be comfortably visible by a user.
[0012] This represents at least 50 adjacent engraved lines (for
example on a 2 cm side) in a direction perpendicular to the main
direction of extension of the array.
[0013] These dimensions also represent the engraving limits of the
tool used to create the engraving. Indeed, when the engravings made
are observed on a microscopic scale, they have a very disturbed
surface condition. The flanks and the engraving backgrounds are not
smooth and have asperities and blisters that are difficult to
control. These defects are formed during the engraving steps, by
partial melting of the laser-engraved material or by beads, milling
residues.
[0014] Moreover, as mentioned above, the relatively large pitch of
displacement of the engraving tool and the resolution, i.e. the
size of the laser "spot"--on the order of 3 to 5 .mu.m--(according
to respective resolutions from 8,000 to 5,080 dpi) limit the
formation of a smooth surface and promote the formation of
contiguous facets rather discontinuous and separated from each
other by rather protruding edges.
[0015] Finally, the dimensions of these structures are adapted to
the medium on which they are applied, i.e. paper. The latter itself
has a certain surface roughness which is on the same order of
magnitude as that of the engraving which leads to a line loss of
the quality of the optical effect sought between the creation of
the structures on a software and the final result.
[0016] A need therefore arose to improve this security element,
aiming in particular at miniaturizing it and maximizing the optical
performances thereof. It is meant by "miniaturization" the
visibility of the optical effect obtained with structures at least
10 times smaller (in width and in height/depth) than those of the
state of the art described above.
[0017] This is particularly interesting when it is desired to use
the security element on a security "thread" or "foil" and no longer
on a printed part of the document. Indeed, in the case of security
threads, when they are "window"-integrated in paper, the visibility
portions of these threads are surfaces of about 2 to 5 mm,
preferably 3 to 4 mm, width to 4 to 14 mm height in general, even
if the tendency is for the maximum increase of these exhibition
surfaces.
[0018] It is meant by "foils" a security element, cold or
preferably hot transferred, directly on the surface of the paper,
in the form of a patch or a stripe (extending over the entire
height of the sheet/banknote).
[0019] A more recent variant exists where the patch or the stripe
extends over a local opening formed in the medium.
[0020] Two main techniques can be envisaged: the hot transfer in
which the carrier film is rewound after the thin film containing
the security elements has been transferred on the medium, and the
lamination where the carrier film of the security elements is
directly deposited on the medium.
[0021] In all cases, if the surfaces delimited by a width and a
length do not represent an issue for the case of a "foil", the
thicknesses available for making the security element according to
the state of the art known in FR-A-2942811 are reduced and do not
exceed a few tens of microns.
[0022] Thus, if the engraving known from the aforementioned
document is used directly on a surface of 0.15 cm.sup.2 (case of
the thread where the average window is of 3.times.5 mm), it would
then be necessary to significantly reduce the number of engraved
lines (more than 5 times less), and this at the expense of the
visibility of the desired visual effect.
[0023] Another strategy would consist in using the same engraving,
i.e. the one and the same engraved line of a width of 400 .mu.m,
but extended over a width of 4 mm. The drawback of this method is
that the angle formed by the flank of the engraving becomes almost
flat, namely less than 1.degree. and not on the order of
30.degree., as it is the case when the width of the line is of 400
.mu.m. Thereby, this loses the effect of changing reflection of
light easily detectable with the naked eye on slopes that have
become almost flat.
[0024] Moreover, the engraving depths taught in this same document
vary from 0 to 200 .mu.m and, in practice, are on the order of 0 to
100 .mu.m.
[0025] These depths are incompatible with a security element in the
form of a thread. Indeed, the thread is inserted into the paper at
the time of its manufacture and must therefore be thin enough for
its thickness not to exceed the thickness of the paper which is of
about 100 .mu.m.
[0026] As a result, the maximum possible thickness for a security
thread, without posing a problem in particular of durability of the
paper in which it is inserted, is on the order of 40 to 50 .mu.m.
And if the functional layers (varnish or protective layer,
laminating glue, thermoadhesives, etc.) are removed from this
thickness, a possible height on the order of a few microns to 30
.mu.m remains for an engraved element. This engraving depth
decrease contributes to flatten the angles if it were to be
transposed to a security thread as it is.
[0027] The same reasoning applies mutatis mutandi for the foil in
particular because of the aforementioned low thicknesses available
which also force the angles to flatten.
[0028] The engraving technique as described in FR-A-2942811 is
therefore not compatible with all the security elements, and in
particular when they are in the form of a thread or a foil.
[0029] The present invention therefore aims in particular at
providing a security element structure which is perfectly suited to
miniaturization, without negative impact on the expected visual
effect and even at improving the latter.
[0030] It also aims at proposing a method for manufacturing such an
element whose flanks and engraving backgrounds as well as the
associated crests are as smooth as possible, i.e. with a minimum of
defects and asperities harmful to the deployment of the light
reflection effects.
SUMMARY OF THE INVENTION
[0031] Thus, the present invention relates to a security element
for a valuable document, which comprises an array (R) of at least
two contiguous or adjacent lines, at least one of these lines being
in relief and having two at least partly opposite inclined flanks
which each originate along one of said longitudinal and opposite
edges of said line, characterized in that said two opposite
inclined flanks meet at a single and uninterrupted sinuous-shaped
junction area which extends along the longitudinal direction of
said line, said flanks having no discontinuity or interruption at
least in said longitudinal direction.
[0032] This security element has a visual effect which results in a
gradual and controlled change of the light reflection upon
inclination of the medium, said light reflection remaining
unchanged even when the size of this security element is
particularly reduced.
[0033] According to other advantageous and non-limiting
characteristics of this security element: [0034] said junction area
has the shape of a sinusoid; [0035] said sinusoid has an unchanged
period over its entire extent; [0036] said sinusoid preferably has
at least one period variation over its extent; [0037] said array
(R) has a non-periodic structure; [0038] the relief of said at
least two lines has a non-periodic variation in height, in width
and/or in length; [0039] said junction area is parallel or
substantially parallel to the plane in which said two longitudinal
and opposite edges are contained; [0040] said junction area is
perpendicular or substantially perpendicular to the plane in which
said two longitudinal and opposite edges are contained; [0041] the
amplitude of said junction area is variable; [0042] the spacing
between said junction area and the plane in which said longitudinal
edges are contained is constant or variable; [0043] said junction
area consists of a ridge or preferably a stripe; [0044] at least
one of said flanks has a rectilinear or non-rectilinear slope;
[0045] all the lines of said array have an identical width; [0046]
said at least two lines have a non-triangular relief profile; in
width and/or in length; [0047] at least one line of said array has
a width different from that of the other lines; [0048] at least one
line of said array has a junction area of a different shape from
that of the other lines; [0049] said flanks are inclined upwards or
downwards, relative to said longitudinal and opposite edges; [0050]
the assembly comprises a multilayer assembly and said array is
integrated in this multilayer assembly, these additional layers
being chosen from the group consisting of the dye or pigment inks,
the color-changing pigment inks, the liquid crystals, the
multilayer plastic films with refractive index variation, the
optical interference filters with thin layers, the vacuum-deposited
metals; [0051] the security element is a security thread, a patch
or a foil.
[0052] The obtained visual effect advantageously comprises at least
one of the following effects: [0053] contrast variation, [0054]
reflection, [0055] interlacing of images, --gray-level image, in
particular through light intensity variations, [0056] movement
and/or displacement of light objects, [0057] images appearing in
one or several plane(s) different from that/those of the
thread.
[0058] The additional layers mentioned above allow adding other
effects to the final structure. It is particularly an effect of
change in color of the structure according to its viewing angle,
this effect is in particular obtained by means of an additional
layer chosen among the color-changing pigment inks, the liquid
crystals, the multilayer plastic films with refractive index
variation and the optical interference filters with thin
layers.
[0059] Another aspect of the invention relates to a method for
manufacturing a security element embossing tool according to any of
the characteristics above.
[0060] This method is remarkable in that it comprises at least the
steps consisting in:
[0061] a) making, i.e. manufacturing, a two-dimensional image
characteristic of a fraction of a line of said array, this image
having multiple levels of gray, a depth or an altitude being
assigned to each gray level;
[0062] b) repeating step a) as much as necessary and assembling
identical or different fractions to form a line of the desired
shape and length;
[0063] c) repeating steps a) and b) as much as necessary to make
lines to be assembled in a contiguous or adjacent manner in order
to form sub-assemblies;
[0064] d) if necessary, repeating steps from a) to c) so as to
achieve the final pattern;
[0065] e) from the image or the final pattern derived from steps a)
to d) above, forming a three-dimensional image in which each point
of this image has a location characteristic of said gray level;
[0066] f) proceeding with the three-dimensional hardware production
thereof, so as to obtain an imprint characteristic of the image
derived from step e).
[0067] According to a particular embodiment, said origination is
carried out by implementing either of the following techniques:
photolithography, in particular gray-level photolithography, laser
lithography, electronic lithography or electron-beam
lithography.
[0068] Finally, the invention relates to a valuable document, in
particular a banknote, which includes at least one security element
according to any of the preceding characteristics.
BRIEF DESCRIPTION OF THE DRAWINGS
[0069] Other characteristics and advantages of the invention will
become apparent upon reading the following description of preferred
embodiments of the invention. This description is made with
reference to the appended drawings in which:
[0070] FIG. 1 is a schematic, three-dimensional and partial view of
an array of lines of a security element according to the
invention;
[0071] FIG. 2 is a view of part of a line of FIG. 1, represented in
"gray levels";
[0072] FIG. 3 is a view of a more extended line of the array of
FIG. 1, represented in "gray levels";
[0073] FIG. 4 is a top view of part of a line of an array according
to one variant of the invention, while FIGS. 4A and 4B are
sectional views of FIG. 4, according to planes the IVA and IVB;
[0074] FIGS. 5 to 10 are schematic views intended to illustrate
some specific shapes of inclined flanks of elements according to
the invention;
[0075] FIG. 11 is a top view of part of a line of an array
according to one variant of the invention, while FIGS. 11A and 11B
are sectional views of FIG. 11, respectively according to the
planes XIA and XIB;
[0076] FIG. 12 is a top view of part of a line of an array
according to one variant of the invention, while FIGS. 12A and 12B
are sectional views of FIG. 12, respectively according to the
planes XIIA and XIIB;
[0077] FIG. 13 is a top view of part of a line of an array
according to one variant of the invention, while FIGS. 13A and 13B
are sectional views of FIG. 13, respectively according to the
planes XIIIA and XIIIB;
[0078] FIG. 14 is a top view of part of a line of an array
according to one variant of the invention, while FIGS. 14A, 14B and
14C are sectional views of FIG. 14, respectively according to the
planes XIVA, XIVB and XIVC;
[0079] FIG. 15 is a top view of part of a line of an array
according to one variant of the invention, while FIGS. 15A, 15B and
15C are sectional views of FIG. 15, respectively according to the
planes XVA, XVB and XVC;
[0080] FIG. 16 is a top view of part of a line of an array
according to one variant of the invention, while FIGS. 16A, 16B and
16C are sectional views of FIG. 16, respectively according to the
planes XVIA, XVIB and XVIC;
[0081] FIG. 17 is a top view of part of a line of an array
according to one variant of the invention, while FIGS. 17A, 17B and
17C are sectional views of FIG. 17, respectively according to the
planes XVIIA, XVIIB and XVIIC;
[0082] FIG. 18 is a top view of part of a line of an array
according to one variant of the invention, while FIGS. 18A and 18B
are sectional views of FIG. 18, respectively according to the
planes XVIIIA and XVIIIB;
[0083] FIG. 19 is a top view of part of a line of an array
according to one variant of the invention, while FIGS. 19A to 19E
are sectional views of FIG. 19, respectively according to the
planes XIXA to XIXE;
[0084] FIG. 20 is a top view of part of a line of an array
according to one variant of the invention, while FIGS. 20A, 20B and
20C are sectional views of FIG. 20, respectively according to the
planes XXA, XXB and XXC;
[0085] FIG. 21 is a top view of part of a line of an array
according to one variant of the invention, while FIGS. 21A and 21B
are sectional views of FIG. 21, respectively according to the
planes XXIA and XXIB;
[0086] FIG. 22 is a top view of part of a line of an array
according to one variant of the invention, while FIGS. 22A and 22B
are sectional views of FIG. 22, respectively according to the
planes XXIIA and XXIIB;
[0087] FIG. 23 is a top view of part of a line of an array
according to one variant of the invention, while FIGS. 23A and 23B
are sectional views of FIG. 23, respectively according to the
planes XXIIIA and XXIIIB;
[0088] FIG. 24 is a top view of part of a line of an array
according to one variant of the invention, while FIGS. 24A and 24B
are sectional views of FIG. 24, respectively according to the
planes XXIVA and XXIVB;
[0089] FIG. 25 is a top view of part of a line of an array
according to one variant of the invention, while FIGS. 25A and 25B
are sectional views of FIG. 25, respectively according to the
planes XXVA and XXVB;
[0090] FIG. 26 is a top view of part of a line of an array
according to one variant of the invention, while FIGS. 26A, 26B and
26C are sectional views of FIG. 26, respectively according to the
planes XXVIA, XXVIB and XXVIC;
[0091] FIG. 27 is a top view of part of a line of an array
according to one variant of the invention, while FIGS. 27A, 27B and
27C are sectional views of FIG. 27, respectively according to the
planes XXVIIA, XXVIIB and XXVIIC;
[0092] FIG. 28 is a top view of part of a line of an array
according to one variant of the invention, while FIGS. 28A, 28B and
28C are sectional views of FIG. 28, respectively according to the
planes XXVIIIA, XXVIIIB and XXVIIIC;
[0093] FIG. 29 is a top view of part of a line of an array
according to one variant of the invention, while FIGS. 29A to 29E
are sectional views of FIG. 29, respectively according to the
planes XXIXA to XXIXE;
[0094] FIG. 30 is a top view of part of a line of an array
according to one variant of the invention, while FIGS. 30A, 30B and
30C are sectional views of FIG. 30, respectively according to the
planes XXXA, XXXB and XXXC;
[0095] FIG. 31 is a top view of part of a line of an array
according to one variant of the invention, while FIGS. 31A, 31B and
31C are sectional views of FIG. 31, respectively according to the
planes XXXIA, XXXIB and XXXIC;
[0096] FIGS. 32 to 36 are schematic sectional views of multilayer
security elements according to the invention;
[0097] FIG. 37 is a top view of a banknote which integrates two
security elements according to the invention;
[0098] Finally, FIGS. 38 to 40 are illustrations of three
embodiments of elements according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0099] FIG. 1 represents a security element according to the
invention.
[0100] This element is only very partially represented so as to
make consultation of the figure easier.
[0101] Thus, this element 1 is formed on a plastic material such as
polyethyleneterephthalate (PET) or bi-oriented polypropylene
(BOPP), without limitation.
[0102] In the example represented here, the element 1 includes an
array R formed of three contiguous lines 2, 2' and 2''. Of course,
it is possible to provide for an element having a much greater
number of lines. The length L of the lines is, in this particular
case, identical and may be on the order of a few millimeters to a
few centimeters. Only a portion is represented here. Likewise, the
width 1 of each of the lines is identical in this particular case
and is comprised between a lower limit which will diffract the
incident light (in the vicinity of 1 .mu.m, which is to be avoided)
and 100 .mu.m to be restricted to a phenomenon of pure reflection,
preferably the upper limit is less than 50 .mu.m and even more
preferably less than 40 .mu.m.
[0103] The height h is, for its part, comprised for example between
1 and 50 .mu.m and preferably on the order of 10 .mu.m or less.
[0104] Of course, in one embodiment not represented, lines of
different widths 1 could be provided.
[0105] In the represented example, the lines 2 to 2'' are
rectilinear. However, in one variant not illustrated in the
figures, the array R can comprise lines having curved, circular and
more generally any shape or even a single, for example
spiral-shaped, line so that the array R is formed by the plurality
of turns of the spiral.
[0106] As clearly visible in the figure, each of the three lines of
the array R is in relief. However, it is possible to envisage that
part of them is in relief while the remaining lines are strictly
planar. Thus, for example, it is possible to envisage an
alternation of relief lines and planar lines. The presence of
non-reflective, in particular transparent, lines could be used to
reveal visually discernible elements of information.
[0107] In the example represented and in accordance with the
invention, each of the relief lines 2 to 2'' has two opposite
inclined flanks 20 and 21 which each originate along one of the
longitudinal and opposite edges 200 and 210 of the line. Here, the
flanks are inclined upwards, which means that they extend towards
each other to a higher altitude than that of the longitudinal edges
200 and 210.
[0108] It is meant throughout the present application by the
expression "inclined flanks" that at least part of at least one of
these two flanks is inclined. In other words, this does not exclude
that the flanks are locally vertical or horizontal.
[0109] Still according to the invention, the two flanks 20 and 21
meet at a single and uninterrupted sinuous-shaped junction area 22
which extends along the longitudinal direction of the line, these
flanks 20 and 21 having no discontinuity or interruption, at least
in the longitudinal direction.
[0110] It is meant by the expression "sinuous-shaped junction area"
that this sinuous junction area does not include any angular area.
In other words, the projection of the junction area in the plane of
the array and the projection of the junction area in the plane
orthogonal to the array and parallel to the lines, are each
described by a continuous function differentiable at any point. In
addition, this junction area is uninterrupted so that it extends in
a unique way from one end to the other of the line in question.
[0111] In the particular embodiment of FIG. 1, the junction area 22
has the shape of a sinusoid and is limited to a line forming a
ridge. In other embodiments, some of which will be described below,
this junction area could consist not of a ridge but of a stripe of
constant or variable width.
[0112] Moreover, this junction area could have a shape different
from that of a sinusoid while remaining sinuous.
[0113] Here, the sinusoid has an unchanged period over its entire
extent. In addition, the adjacent lines are in phase (parallel
evolution of the junction areas), but it could of course be
otherwise. Moreover, its amplitude is equal to the width 1 of the
line. Here again, it could be otherwise. Particularly, the sinusoid
may have a variable period, the adjacent lines may have a phase
shift, and/or the amplitude of the sinusoid is different from the
width of the lines.
[0114] Finally, it is noted that the plane in which this sinusoid
extends is parallel to the plane P which contains the two
longitudinal edges 200 and 210. Again, it could be otherwise, as
will be shown with reference to other figures.
[0115] Furthermore, it is noted that the flanks 20 and 21 of each
line have a rectilinear slope from one of the longitudinal edges
towards the junction area 22.
[0116] FIG. 2 represents only one of the lines of the array R of
FIG. 1. Furthermore, this line is represented in "gray levels".
This means that a shade comprised between white and black has been
assigned to each point of this line by taking into account the rule
according to which the more the point of this line is distant from
the aforementioned plane P, the darker its color. Thus, the area 22
is represented in black color. This representation in gray levels
is used for the manufacture of the present security element, as
will be shown later in the description.
[0117] FIG. 3 is a view equivalent to FIG. 2, except that a line 2
having a greater longitudinal extent has been represented.
[0118] FIG. 4 represents a top view of the line of FIGS. 2 and 3,
and limited to the representation of a single period of the
sinusoid. It is even easier to distinguish the different variations
of gray, depending on the considered location. The section of FIG.
4A explicitly shows that, in this region, the junction area 22 is
located at the vertical of the longitudinal edge 200. This figure
also shows that the flank 21 has a rectilinear slope.
[0119] FIG. 4B illustrates, for its part, the fact that, according
to the cutting plane illustrated here, the junction area 22 is
located halfway between the two longitudinal edges 200 and 210. The
straight line which is located at the vertical of the area 22 is
referenced 23, however without this straight line existing in
reality.
[0120] FIG. 5 is similar to FIG. 4A and emphasizes the fact that
the flank 21 has a rectilinear slope. In this figure et seq., the
reference h designates the maximum height of the sinusoid 22.
[0121] FIGS. 6 to 10 represent general shapes (sections) different
from the flank 21, without this constituting an exhaustive panel.
However, it should be specified that these descriptions are also
valid for the second flank 20 which has not been represented here.
Of course, the flanks 20 and 21 can have different general
shapes.
[0122] Thus, in FIG. 6, the flank 21 has a slope which is slightly
convex, whose convexity is directed away from the base of the
flank.
[0123] Conversely, FIG. 7 deals with a flank 21 whose slope has a
slight concavity directed towards the base of the flank.
[0124] FIGS. 8 to 10 represent embodiments based on those that have
just been described.
[0125] Thus, more specifically, FIG. 8 represents the situation in
which the flank 21 falls within a straight line but has locally a
slight concavity (trough) referenced 24 as well as a slight
convexity (boss) referenced 25.
[0126] FIG. 9 illustrates a flank 21 which is generally convex but
which has a point of inflection, i.e. a change in curvature,
towards the edge 210.
[0127] As for FIG. 10, it deals here with a flank 21 of a shape
generally similar to that of FIG. 9 but with, locally, a slight
concavity (trough) referenced 24 as well as a slight convexity
(boss) 25.
[0128] These bosses or "growths" and troughs or "hollows" generate,
within the element, specific reflective aspects of light, in order
to reveal information that stands out from the background according
to the viewing angle.
[0129] FIG. 11 is a view similar to FIG. 4 of one variant. Here
again, it deals with a junction area 22 which has the shape of a
sinusoid whose amplitude is equal to the width 1 of the line.
However, it will be noted on observation of FIGS. 11A and 11B that
the two flanks 20 and 21 have a convex-shaped slope.
[0130] FIG. 12 deals with one variant of FIG. 11 in which, as shown
in FIGS. 12A and 12B, the flanks 20 and 21 have a concave-shaped
slope.
[0131] The embodiment of FIG. 13 still deals with a junction area
which has the shape of a sinusoid. However, here its amplitude is
smaller than the width 1 of the line. In addition, its flanks 20
and 21 have a slope comprising one or two rectilinear portions, as
shown in FIG. 13B. Indeed, in some areas of this line, each flank
20 and 21 has a part of attachment to the edges 200 and 210 which
is coincident with the aforementioned plane P.
[0132] The embodiments which have just been described had in common
that the junction area 22 is parallel to the plane P in which the
longitudinal edges 200 and 210 are contained.
[0133] This is not the case with FIG. 14 in particular. Indeed, in
this embodiment, if the junction area 22 still falls within a
sinusoid, the latter is deployed in a plane perpendicular or
substantially perpendicular to the aforementioned plane P.
[0134] The consultation of FIGS. 14A to 14C shows that the flanks
20 and 21 meet the opposite edges 200 and 210, these flanks having
a slope of curved shape with a point of inflection.
[0135] The embodiment of FIG. 15 substantially deals with the same
characteristics as in the variant of FIG. 14. However, the
amplitude of the sinusoid is slightly smaller and the flanks 20 and
21 have a slightly concave shape.
[0136] Likewise, the variant of FIGS. 16, 16A, 16B and 16C
substantially deals with the embodiments of FIG. 14 et seq. except
that the maximum altitude of the junction area 22 remains stable
over a certain extent, so that it gives it the form of a
plateau.
[0137] In the embodiments which have just been described, the
junction area 22 was always overhanging relative to the locations
from where the flanks 20 and 21 originate.
[0138] This is not the situation illustrated in FIG. 17 in which
the junction area 22 is still located at a level lower than that of
the flanks 20 and 21. This area has the shape of a sinusoid whose
amplitude is smaller than the width of the line. In addition, its
"altitude", i.e. its distance with respect to the plane P is not
constant, as shown in FIGS. 17A and 17B.
[0139] FIG. 18 represents a situation relatively similar to that of
FIG. 17. Again, the amplitude of the junction area 22 is smaller
than the width 1 of the line, and the flank 21 has here, locally, a
level difference located in the form of a trough and referenced
24.
[0140] FIG. 19 schematically represents the situation in which the
junction area still has the shape of a sinusoid. However, it is not
deployed in a plane strictly parallel to the plane P in which the
longitudinal edges 200 and 210 are contained. More specifically, as
one advances in the longitudinal extent of this line, said junction
area approaches the aforementioned plane P.
[0141] The embodiment of FIG. 20 deals with a junction area which
still falls within a sinusoid. However, this junction area has the
shape of a stripe, i.e. it is not materialized by a ridge but has a
non-negligible transverse extent, as shown in particular in FIG.
20A.
[0142] FIG. 21 illustrates a situation comparable to that of FIG.
4. However, it will be noted that the sinusoidal junction area 22
has an amplitude which is still smaller than the width of the line
and is centered on this line so that the flanks 20 and 21 are each
bordered towards the longitudinal edges 200 and 210 by strictly
planar areas coincident with the aforementioned plane P.
[0143] FIG. 22 deals with a junction area 22 which is still
recessed relative to the flanks 20 and 21, as shown particularly in
FIGS. 22A and 22B. On the other hand, the amplitude of this
junction area is still equal to the width of the line.
[0144] This is not the case with FIG. 23 where the sinusoidal
junction area 22 has an amplitude smaller than the width of the
line. In addition, here again, this junction area is recessed
relative to the flanks 20 and 21.
[0145] FIG. 24 deals with a sinusoidal junction area 22 whose
amplitude is smaller than the width of the line. Moreover and as
shown in the two sectional views of FIGS. 24A and 24B, the flanks
20 and 21 locally have either a horizontal orientation (in the form
of a plateau) or the combination of a horizontal and oblique
(inclined) orientation.
[0146] FIG. 25 represents a shape of a sinusoidal junction area 22
relatively similar to that of FIG. 23. However, as can be observed
from the reading of FIG. 25B, in some regions of the longitudinal
extent of the line, the flanks 20 and 21 each comprise two
rectilinear portions of different orientation.
[0147] FIG. 26 represents one embodiment which is exactly the
inverse of that of FIG. 14. This means that the sinusoidal junction
area 22 is deployed in a plane parallel to the planes that contain
the edges 200 and 210. However, the flanks 20 and 21 are still
raised relative to said junction area.
[0148] FIG. 27 represents a situation relatively similar to that of
FIG. 26, except that the period and the amplitude of the sinusoid
which constitutes the junction area 22 are different.
[0149] FIG. 28 represents an embodiment very similar to that of
FIG. 27. It is distinguished by the fact that the flanks 20 and 21,
instead of being convex, are concave.
[0150] FIG. 29 is composed of a unit module mirrored horizontally
and vertically. This base module has four corners. An altitude has
been set at each corner of this base module. The opposite corners
are at the same altitude. Two are at maximum altitude and two are
at minimum altitude. This module therefore looks like an "X" whose
two opposite tips go up and the two others go down.
[0151] FIG. 30 illustrates the case where the sinusoid is not
centered in the block. The junction area 22 has a continuous but
irregular shape. The flanks 20 and 21 have a variable amplitude
depending on their position on the block. Thus, in the sectional
view represented in FIG. 30A, the flanks 20 and 21 consist of
plateaus and perfectly symmetrical increases/decreases, whereas in
the sectional view represented in FIG. 30B, the plateaus and slopes
of the flanks 20 and 21 are not symmetrical, thus generating a more
or less narrow valley effect.
[0152] Finally, the embodiment of FIG. 31 still deals with a
sinusoidal junction area. It extends in a plane parallel to the
aforementioned plane P but it is noted, in particular by comparing
FIGS. 31 and 31C, that the period of this sinusoid varies according
to the longitudinal extent of the line.
[0153] After having described these different embodiments of the
security element 1 according to the invention, let us now proceed
to the description of at least one example of manufacture of an
imprint of such a security element.
[0154] For this description, reference will be made more
specifically to FIGS. 1, 2, 3 and 4.
[0155] Thus, in a first step, this method consists in making, i.e.
in manufacturing, a two-dimensional image which is characteristic
of a fraction of a line of the array R to be constituted, this
image having "multiple levels of gray", a depth or an altitude
being assigned to each gray level.
[0156] Preferably, this first step makes use of vector or raster
graphical tools, such as currently available software. A
two-dimensional image is thus obtained where the unit segment is
here the period characteristic of the sinusoid. This unit segment
will be replicated in a manner similar to what is visible in the
abovementioned FIGS. 3 and 4 or adjoined to a new segment so that
the effect obtained is visually continuous and devoid of visible
connection point. At least two identical or different unit segments
form a first block or a first fraction to be replicated as many
times as desired.
[0157] In a second step, the step which has just been described is
repeated as many times as necessary and different unit segments
and/or identical or different blocks or fractions are assembled to
form a line of the desired shape and length. Of course, in order to
maintain the continuity of the design, it is made sure that the
starting and ending points of the junction area of each of the
blocks connect to each other without a visible connection
point.
[0158] This applies, of course, even if the junction area extends
in a plane perpendicular to the aforementioned plane P.
[0159] In a subsequent step, the previous steps are repeated as
many times as necessary to make several lines to be assembled in a
contiguous or adjacent manner in order to constitute sub-assemblies
able to generate optical effects discernible with the naked eye.
The lines of the array R of a sub-assembly could be identical or
different. Finally, the whole is repeated again so as to achieve,
if this is the objective that has been set out, the final pattern
with these sub-assemblies. It is noted that it is meant here by
"sub-assembly" a three-dimensional structure whose optical effects
are sufficient in themselves in that they are remarkable and in
that the assembly of identical or different sub-assemblies can be
made with discontinuity in the connections (non-continuity of the
lines, sudden change of inflection or even total disconnection but
small enough to be indiscernible to the naked eye). According to a
preferred variant, said assembly of identical or different
sub-assemblies is made with continuity in the connections.
[0160] In a subsequent step, and based on what has just been
described, a three-dimensional image in which each point of this
image has a location characteristic of the gray level is made,
still with vector graphical tools. This image is then encoded in
the specific language of the tool generating the actual engraving
elements in order to be recorded therein in the form of an imprint
in an engravable medium.
[0161] By way of example and without limitation, each line obtained
has the configuration of FIG. 3.
[0162] A following step of this method consists in implementing the
origination of a photosensitive resin by three-dimensional
engraving thereof, with a view to obtaining an engraving
characteristic of the image derived from the previous step.
[0163] This origination can be implemented in particular by the
following techniques: [0164] a) the photolithography or optical
projection-lithography: [0165] This involves exposing a
photosensitive resin to photons through a mask. In the exposed
areas, the photons modify the solubility of the resin. If the resin
is positive, the exposed area is removed during the development
while, if it is negative, the exposed area is maintained during
this development; [0166] b) the gray-level photolithography: [0167]
In this particular case, the mask is a gray-level mask, therefore
the densities of opaque pixels are on a transparent background, the
more or less exposed parts making it possible to manage different
step heights; [0168] c) the laser-lithography [0169] This technique
is interesting since there is no use of a mask. Lasers, such as UV,
nanosecond pulsed, excimer, NdYAG, picosecond or femtosecond
lasers, are used in direct use on the resin. [0170] The resolution
is on the order of 0.8 .mu.m. [0171] d) the electronic lithography
or electron beam (e-beam) lithography: [0172] This involves is a
maskless technique in which the patterns are created by direct
scanning of an electron beam (10 to 100 electronvolts) in the resin
film. The resolution is equal to the diameter of the electron beam,
which represents a few nanometers. The engraving depth is given by
the penetration of the electrons, which is of 100 nm.
[0173] What these technologies have in common is that they allow
obtaining almost smooth and planar engravings. In other words,
given the very small pitch of the tool (from a few nanometers to
0.8 .mu.m), the engraving background but also the engraving flank
can be almost devoid of asperities, at least compared to the
aforementioned state of the art.
[0174] However, if surface irregularities were still present
damaging the production and legibility of the desired optical
effects, it would be possible to envisage a micropolishing. A
single mirror which extends along an engraving direction and which
is curved in the shape of a flank whose angles vary continuously is
then obtained in each line.
[0175] The subsequent steps of manufacturing the embossing elements
(such as plates) are relatively conventional and require the
transformation (electrodeposition, recombination, chromium plating,
etc.) of the unitary element created during the origination step up
to the multiple-up tool which will be used for a thermoplastic
embossing or for a UV-assisted embossing by the technique called
"Nano Imprint" lithography.
[0176] In the foregoing, there is just a description of a
single-layer security element. However, in a good number of
situations, this security element will be a multilayer security
element and it is proposed to describe some embodiments thereof,
most particularly with reference to FIGS. 32 to 36.
[0177] Thus, the embodiment of FIG. 32 deals with an assembly E
which has a security element 1 according to the invention
consisting of a plastic film 3 covered by an embossable varnish 4.
Thin chromium 5, silica oxide 6 and aluminum 7 layers are
successively deposited on this security element and this by way of
illustration only. Of course, other thin film stacks with other
materials and/or a different number of layers can be envisaged to
produce remarkable visual effects. The localized removal of part of
the aluminum 7 is then carried out to create openings 70.
[0178] According to this variant, the observer who looks at this
assembly through the film 3 will notice the combination of several
optical effects. Thus, the layers 5, 6 and 7 cause effects of
change in color of the structure according to its viewing angle,
for example from magenta to green. This color change effect is
associated with the progressive variations of the angle of the
curved mirror consisting of the security element 1, which causes a
synergy effect in which the hollow of the engravings is tinted with
a uniform color, while the flanks gradually change color to a green
tint. It is noted here that the security element 1 is represented
rotated at 90.degree. from reality to be in order to be located in
the plane of the figure, for the purpose of good understanding.
[0179] The embodiment of FIG. 33 deals successively, from top to
bottom, with a plastic film 3, an embossable varnish 4, an aluminum
layer 7 having openings 70, a silicon oxide layer 6 and a chromium
layer 5. The security element 1 is made on this assembly of
superimposed layers.
[0180] Yet another assembly E is represented in FIG. 34, the
viewing side being that of the thin chromium layer 5.
[0181] The embodiment of FIG. 35 deals with a medium 3 which
includes therein or on its surface a color change effect. This
comprises a multilayer material with refractive index variation or
at least one liquid crystal ink. This medium is coated with a
varnish 1 which is deformed during its application by micro
replication in the UV-assisted wet state (or Nano Imprint), so that
the shape of the engraved tool reproduces its imprint in the
varnish. The varnish is then covered with a colored, for example
black, layer 7 so as to reveal, during an observation through the
medium and in line with the printed areas 71, a combined effect of
color change and curved mirror. In the openings 70 corresponding to
areas not coated with black ink, a clear and transparent text
effect is achieved.
[0182] In the embodiment of FIG. 36, the varnish medium 3 is
interposed between the security element 1 and the layer 7. In
addition, an additional layer 6 whose refractive index is
sufficiently different from that of the varnish of the varnish
medium 3 is provided rearwardly of the element 1. This layer is
preferably chosen among varnishes with high refractive index, for
example of the ZnS type, or with low refractive index, of the
perfluoropolyether type.
[0183] Of course, additional layers used for the manufacture of
security elements such as threads, like the camouflage layers,
laminating layers with another plastic medium or thermoadhesive
layers, protective layers, adhesive layers, have not been
represented in the figures which have just been described, for the
sake of simplification.
[0184] FIG. 37 deals with a banknote which has two security
elements according to the invention, namely in the left part a
security element 1 which has the shape of a rectangular block (a
patch), and to the right an element 1 in the form of a windowed
security thread.
[0185] FIG. 38 shows an example of a security element 1 according
to the teachings of the present invention, which represents a
square-shaped pattern consisting of a series of sub-assemblies of
ten lines whose sinusoids are in phase relative to each other to
form the array R. Each of these sub-assemblies is shifted
vertically relative to its left and right neighbors. This shift is
regular until the middle of the image where it is inverted. This
results in a macroscopic effect of herringbones capable of moving
according to the inclination of the medium on which the element 1
is introduced/affixed.
[0186] FIG. 39 shows a second example of a security element 1
according to the teachings of the present invention, which
represents a square-shaped pattern consisting of a series of
sub-assemblies forming waves stylized in the manner of "The Great
Wave off Kanagawa" from Hokusai.
[0187] In this particular case, a wave consists of two
sub-assemblies. The first sub-assembly consists of curved lines
whose interior widens through a maximum. A second sub-assembly is
adjoined thereto and its lines are curved in the same direction as
the first one, but the interior narrows through a minimum. This
pair of adjoined sub-assemblies is repeated and ordered in a tiling
which allows not leaving a gap therebetween. This results in a
macroscopic effect of waves capable of moving according to the
inclination of the medium on which the element 1 is
introduced/affixed.
[0188] Finally, FIG. 40 shows a third example of a security element
1 in accordance with the teachings of the present invention, which
represents a square-shaped pattern consisting of a series of
sub-assemblies forming patterns of stylized boats sailing on an
expanse of water. The expanse of water is built in the manner of
FIG. 38 and the boats are built in the manner of FIG. 39, in
particular with a first sub-assembly consisting of curved lines
whose interior widens through a maximum forming the hull and,
identically, another sub-assembly reproducing the sail. All these
sub-assemblies are superimposed to form the overall image
represented in FIG. 40.
[0189] These last three figures show a slight overview of the
possibilities of creation. The possibilities of arrangement of
these sub-assemblies are virtually endless, so that it is possible
to make any type of more or less figurative, more or less stylized
image.
* * * * *